1. Field
One embodiment of the invention relates to a storage device including a cache, and an information processing apparatus including the storage device.
2. Description of the Related Art
In recent years, various types of personal computers, such as notebook type personal computers and desktop type personal computers, have widely been used. Most of personal computers include hard disk drives (HDDs) as external storage devices.
In addition, recently, in order to improve the responsivity of the HDD, various proposals have been made of so-called hybrid HDDs in which nonvolatile memories functioning as caches are incorporated.
Jpn. Pat. Appln. KOKAI Publication No. H11-306664, for instance, discloses a technique for reducing the power consumption of a storage device such as an HDD. In an external storage device which is disclosed in KOKAI No. H11-306664, the spindle motor is turned off when access to the external storage device from a host device is absent for a predetermined time.
By turning off the spindle motor, the power consumption of the external storage device can be reduced. However, in a case where an access request is issued from the host device in the state in which the spindle motor is turned off, the access to a disk storage medium has to stand by until the spindle motor is turned on and the disk storage medium begins to rotate at a normal rotational speed. Thus, frequent turn-off of the spindle motor may become a factor which deteriorates the responsivity of the external storage medium.
Therefore, it is necessary to realize a novel function which can satisfy demands of both a user who places priority on the responsivity by the sacrifice of the power consumption, and a user who places priority on the power consumption by the sacrifice of the responsivity.